Drug/drug delivery systems for the prevention and treatment of vascular disease

ABSTRACT

A drug and drug delivery system may be utilized in the treatment of vascular disease. A local delivery system is coated with rapamycin or other suitable drug, agent or compound and delivered intraluminally for the treatment and prevention of neointimal hyperplasia following percutaneous transluminal coronary angiography. The local delivery of the drugs or agents provides for increased effectiveness and lower systemic toxicity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/850,365 filed on May 7, 2001 now abandoned, which is acontinuation-in-part application of U.S. application Ser. No.09/575,480, filed on May 19, 2000, U.S. Pat. No. 8,029,561 which claimsthe benefit of U.S. Provisional Application No. 60/204,417, filed May12, 2000 and claims the benefit of U.S. Provisional Application No.60/262,614, filed Jan. 18, 2001, U.S. Provisional Application No.60/262,461, filed Jan. 18, 2001, U.S. Provisional Application No.60/263,806, filed Jan. 24, 2001 and U.S. Provisional Application No.60/263,979, filed Jan. 25, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to drugs and drug delivery systems for theprevention and treatment of vascular disease, and more particularly todrugs and drug delivery systems for the prevention and treatment ofneointimal hyperplasia.

2. Discussion of the Related Art

Many individuals suffer from circulatory disease caused by a progressiveblockage of the blood vessels that perfuse the heart and other majororgans with nutrients. More severe blockage of blood vessels in suchindividuals often leads to hypertension, ischemic injury, stroke, ormyocardial infarction. Atherosclerotic lesions, which limit or obstructcoronary blood flow, are the major cause of ischemic heart disease.Percutaneous transluminal coronary angioplasty is a medical procedurewhose purpose is to increase blood flow through an artery. Percutaneoustransluminal coronary angioplasty is the predominant treatment forcoronary vessel stenosis. The increasing use of this procedure isattributable to its relatively high success rate and its minimalinvasiveness compared with coronary bypass surgery. A limitationassociated with percutaneous transluminal coronary angioplasty is theabrupt closure of the vessel which may occur immediately after theprocedure and restenosis which occurs gradually following the procedure.Additionally, restenosis is a chronic problem in patients who haveundergone saphenous vein bypass grafting. The mechanism of acuteocclusion appears to involve several factors and may result fromvascular recoil with resultant closure of the artery and/or depositionof blood platelets and fibrin along the damaged length of the newlyopened blood vessel.

Restenosis after percutaneous transluminal coronary angioplasty is amore gradual process initiated by vascular injury. Multiple processes,including thrombosis, inflammation, growth factor and cytokine release,cell proliferation, cell migration and extracellular matrix synthesiseach contribute to the restenotic process.

While the exact mechanism of restenosis is not completely understood,the general aspects of the restenosis process have been identified. Inthe normal arterial wall, smooth muscle cells proliferate at a low rate,approximately less than 0.1 percent per day. Smooth muscle cells in thevessel walls exist in a contractile phenotype characterized by eighty toninety percent of the cell cytoplasmic volume occupied with thecontractile apparatus. Endoplasmic reticulum, Golgi, and free ribosomesare few and are located in the perinuclear region. Extracellular matrixsurrounds the smooth muscle cells and is rich in heparin-likeglycosylaminoglycans which are believed to be responsible formaintaining smooth muscle cells in the contractile phenotypic state(Campbell and Campbell, 1985).

Upon pressure expansion of an intracoronary balloon catheter duringangioplasty, smooth muscle cells within the vessel wall become injured,initiating a thrombotic and inflammatory response. Cell derived growthfactors such as platelet derived growth factor, fibroblast growthfactor, epidermal growth factor, thrombin, etc., released fromplatelets, invading macrophages and/or leukocytes, or directly from thesmooth muscle cells provoke proliferative and migratory responses inmedial smooth muscle cells. These cells undergo a change from thecontractile phenotype to a synthetic phenotype characterized by only afew contractile filament bundles, extensive rough endoplasmic reticulum,Golgi and free ribosomes. Proliferation/migration usually begins withinone to two days post-injury and peaks several days thereafter (Campbelland Campbell, 1987; Clowes and Schwartz, 1985).

Daughter cells migrate to the intimal layer of arterial smooth muscleand continue to proliferate and secrete significant amounts ofextracellular matrix proteins. Proliferation, migration andextracellular matrix synthesis continue until the damaged endotheliallayer is repaired at which time proliferation slows within the intima,usually within seven to fourteen days post-injury. The newly formedtissue is called neointima. The further vascular narrowing that occursover the next three to six months is due primarily to negative orconstrictive remodeling.

Simultaneous with local proliferation and migration, inflammatory cellsinvade the site of vascular injury. Within three to seven dayspost-injury, inflammatory cells have migrated to the deeper layers ofthe vessel wall. In animal models employing either balloon injury orstent implantation, inflammatory cells may persist at the site ofvascular injury for at least thirty days (Tanaka et al., 1993; Edelmanet al., 1998). Inflammatory cells therefore are present and maycontribute to both the acute and chronic phases of restenosis.

Numerous agents have been examined for presumed anti-proliferativeactions in restenosis and have shown some activity in experimentalanimal models. Some of the agents which have been shown to successfullyreduce the extent of intimal hyperplasia in animal models include:heparin and heparin fragments (Clowes, A. W. and Karnovsky M., Nature265: 25-26, 1977; Guyton, J. R. et al., Circ. Res., 46: 625-634, 1980;Clowes, A. W. and Clowes, M. M., Lab. Invest. 52: 611-616, 1985; Clowes,A. W. and Clowes, M. M., Circ. Res. 58: 839-845, 1986; Majesky et al.,Circ. Res. 61: 296-300, 1987; Snow et al., Am. J. Pathol. 137: 313-330,1990; Okada, T. et al., Neurosurgery 25: 92-98, 1989), colchicine(Currier, J. W. et al., Circ. 80: 11-66, 1989), taxol (Sollot, S. J. etal., J. Clin. Invest. 95: 1869-1876, 1995), angiotensin convertingenzyme (ACE) inhibitors (Powell, J. S. et al., Science, 245: 186-188,1989), angiopeptin (Lundergan, C. F. et al. Am. J. Cardiol. 17(Suppl.B):132B-136B, 1991), cyclosporin A (Jonasson, L. et al., Proc. Natl.,Acad. Sci., 85: 2303, 1988), goat-anti-rabbit PDGF antibody (Ferns, G.A. A., et al., Science 253: 1129-1132, 1991), terbinafine (Nemecek, G.M. et al., J. Pharmacol. Exp. Thera. 248: 1167-1174, 1989), trapidil(Liu, M. W. et al., Circ. 81: 1089-1093, 1990), tranilast (Fukuyama, J.et al., Eur. J. Pharmacol. 318: 327-332, 1996), interferon-gamma(Hansson, G. K. and Holm, J., Circ. 84:1266-1272, 1991), rapamycin(Marx, S. O. et al., Circ. Res. 76: 412-417, 1995), corticosteroids(Colburn, M. D. et al., J. Vasc. Surg. 15: 510-518, 1992), see alsoBerk, B. C. et al., J. Am. Coll. Cardiol. 17: 111B-117B, 1991), ionizingradiation (Weinberger, J. et al., Int. J. Rad. Onc. Biol. Phys. 36:767-775, 1996), fusion toxins (Farb, A. et al., Circ. Res. 80: 542-550,1997) antisense oligonucleotides (Simons, M. et al., Nature 359: 67-70,1992) and gene vectors (Chang, M. W. et al., J. Clin. Invest. 96:2260-2268, 1995). Anti-proliferative effects on smooth muscle cells invitro have been demonstrated for many of these agents, including heparinand heparin conjugates, taxol, tranilast, colchicine, ACE inhibitors,fusion toxins, antisense oligonucleotides, rapamycin and ionizingradiation. Thus, agents with diverse mechanisms of smooth muscle cellinhibition may have therapeutic utility in reducing intimal hyperplasia.

However, in contrast to animal models, attempts in human angioplastypatients to prevent restenosis by systemic pharmacologic means have thusfar been unsuccessful. Neither aspirin-dipyridamole, ticlopidine,anti-coagulant therapy (acute heparin, chronic warfarin, hirudin orhirulog), thromboxane receptor antagonism nor steroids have beeneffective in preventing restenosis, although platelet inhibitors havebeen effective in preventing acute reocclusion after angioplasty (Makand Topol, 1997; Lang et al., 1991; Popma et al., 1991). The platelet GPIIb/IIIa receptor, antagonist, Reopro is still under study but has notshown promising results for the reduction in restenosis followingangioplasty and stenting. Other agents, which have also beenunsuccessful in the prevention of restenosis, include the calciumchannel antagonists, prostacyclin mimetics, angiotensin convertingenzyme inhibitors, serotonin receptor antagonists, andanti-proliferative agents. These agents must be given systemically,however, and attainment of a therapeutically effective dose may not bepossible; anti-proliferative (or anti-restenosis) concentrations mayexceed the known toxic concentrations of these agents so that levelssufficient to produce smooth muscle inhibition may not be reached (Makand Topol, 1997; Lang et al., 1991; Popma et al., 1991).

Additional clinical trials in which the effectiveness for preventingrestenosis utilizing dietary fish oil supplements or cholesterollowering agents has been examined showing either conflicting or negativeresults so that no pharmacological agents are as yet clinicallyavailable to prevent post-angioplasty restenosis (Mak and Topol, 1997;Franklin and Faxon, 1993: Serruys, P. W. et al., 1993). Recentobservations suggest that the antilipid/antioxidant agent, probucol maybe useful in preventing restenosis but this work requires confirmation(Tardif et al., 1997; Yokoi, et al., 1997). Probucol is presently notapproved for use in the United States and a thirty-day pretreatmentperiod would preclude its use in emergency angioplasty. Additionally,the application of ionizing radiation has shown significant promise inreducing or preventing restenosis after angioplasty in patients withstents (Teirstein et al., 1997). Currently, however, the most effectivetreatments for restenosis are repeat angioplasty, atherectomy orcoronary artery bypass grafting, because no therapeutic agents currentlyhave Food and Drug Administration approval for use for the prevention ofpost-angioplasty restenosis.

Unlike systemic pharmacologic therapy, stents have proven effective insignificantly reducing restenosis. Typically, stents areballoon-expandable slotted metal tubes (usually, but not limited to,stainless steel), which, when expanded within the lumen of anangioplastied coronary artery, provide structural support through rigidscaffolding to the arterial wall. This support is helpful in maintainingvessel lumen patency. In two randomized clinical trials, stentsincreased angiographic success after percutaneous transluminal coronaryangioplasty, by increasing minimal lumen diameter and reducing, but noteliminating, the incidence of restenosis at six months (Serruys et al.,1994; Fischman et al., 1994).

Additionally, the heparin coating of stents appears to have the addedbenefit of producing a reduction in sub-acute thrombosis after stentimplantation (Serruys et al., 1996). Thus, sustained mechanicalexpansion of a stenosed coronary artery with a stent has been shown toprovide some measure of restenosis prevention, and the coating of stentswith heparin has demonstrated both the feasibility and the clinicalusefulness of delivering drugs locally, at the site of injured tissue.

Accordingly, there exists a need for effective drugs and drug deliverysystems for the effective prevention and treatment of neointimalthickening that occurs after percutaneous transluminal coronaryangioplasty and stent implantation.

SUMMARY OF THE INVENTION

The drugs and drug delivery systems of the present invention provide ameans for overcoming the difficulties associated with the methods anddevices currently in use as briefly described above.

In accordance with one aspect, the present invention is directed to amethod for the treatment of intimal hyperplasia in vessel walls. Themethod comprises the controlled delivery, by release from anintraluminal medical device, of cell cycle inhibitors that actselectively at the G1 phase of the cell cycle.

In accordance with another aspect, the present invention is directed toa drug delivery device. The drug delivery device comprises anintraluminal medical device and a therapeutic dosage of an agentreleasably affixed to the intraluminal medical device for the treatmentof intimal hyperplasia, constrictive vascular remodeling andinflammation caused by injury.

The drugs and drug delivery systems of the present invention utilize astent or graft in combination with rapamycin or otherdrugs/agents/compounds to prevent and treat neointimal hyperplasia, i.e.restenosis, following percutaneous transluminal coronary angioplasty andstent implantation. It has been determined that rapamycin functions toinhibit smooth muscle cell proliferation through a number of mechanisms.It has also been determined that rapamycin eluting stent coatingsproduce superior effects in humans, when compared to animals, withrespect to the magnitude and duration of the reduction in neointimalhyperplasia. Rapamycin administration from a local delivery platformalso produces an anti-inflammatory effect in the vessel wall that isdistinct from and complimentary to its smooth muscle cellanti-proliferative effect. In addition, it has also been demonstratedthat rapamycin inhibits constrictive vascular remodeling in humans.

Other drugs, agents or compounds which mimic certain actions ofrapamycin may also be utilized in combination with local deliverysystems or platforms.

The local administration of drugs, agents or compounds to stentedvessels have the additional therapeutic benefit of higher tissueconcentration than that which would be achievable through the systemicadministration of the same drugs, agents or compounds. Other benefitsinclude reduced systemic toxicity, single treatment, and ease ofadministration. An additional benefit of a local delivery device anddrug, agent or compound therapy may be to reduce the dose of thetherapeutic drugs, agents or compounds and thus limit their toxicity,while still achieving a reduction in restenosis.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 is a chart indicating the effectiveness of rapamycin as ananti-inflammatory relative to other anti-inflammatories.

FIG. 2 is a view along the length of a stent (ends not shown) prior toexpansion showing the exterior surface of the stent and thecharacteristic banding pattern.

FIG. 3 is a perspective view of the stent of FIG. 1 having reservoirs inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As stated above, the proliferation of vascular smooth muscle cells inresponse to mitogenic stimuli that are released during balloonangioplasty and stent implantation is the primary cause of neointimalhyperplasia. Excessive neointimal hyperplasia can often lead toimpairment of blood flow, cardiac ischemia and the need for a repeatintervention in selected patients in high risk treatment groups. Yetrepeat revascularization incurs risk of patient morbidity and mortalitywhile adding significantly to the cost of health care. Given thewidespread use of stents in interventional practice, there is a clearneed for safe and effective inhibitors of neointimal hyperplasia.

Rapamycin is a macroyclic triene antibiotic produced by streptomyceshygroscopicus as disclosed in U.S. Pat. No. 3,929,992. It has been foundthat rapamycin inhibits the proliferation of vascular smooth musclecells in vivo. Accordingly, rapamycin may be utilized in treatingintimal smooth muscle cell hyperplasia, restenosis and vascularocclusion in a mammal, particularly following either biologically ormechanically mediated vascular injury, or under conditions that wouldpredispose a mammal to suffering such a vascular injury. Rapamycinfunctions to inhibit smooth muscle cell proliferation and does notinterfere with the re-endothelialization of the vessel walls.

Rapamycin functions to inhibit smooth muscle cell proliferation througha number of mechanisms. In addition, rapamycin reduces the other effectscaused by vascular injury, for example, inflammation. The operation andvarious functions of rapamycin are described in detail below. Rapamycinas used throughout this application shall include rapamycin, rapamycinanalogs, derivatives and congeners that bind FKBP12 and possess the samepharmacologic properties as rapamycin.

Rapamycin reduces vascular hyperplasia by antagonizing smooth muscleproliferation in response to mitogenic signals that are released duringangioplasty. Inhibition of growth factor and cytokine mediated smoothmuscle proliferation at the late G1 phase of the cell cycle is believedto be the dominant mechanism of action of rapamycin. However, rapamycinis also known to prevent T-cell proliferation and differentiation whenadministered systemically. This is the basis for its immunosuppresiveactivity and its ability to prevent graft rejection.

The molecular events that are responsible for the actions of rapamycin,a known anti-proliferative, which acts to reduce the magnitude andduration of neointimal hyperplasia, are still being elucidated. It isknown, however, that rapamycin enters cells and binds to a high-affinitycytosolic protein called FKBP12. The complex of rapamycin and FKPB12 inturn binds to and inhibits a phosphoinositide (PI)-3 kinase called the“mammalian Target of Rapamycin” or TOR. TOR is a protein kinase thatplays a key role in mediating the downstream signaling events associatedwith mitogenic growth factors and cytokines in smooth muscle cells and Tlymphocytes. These events include phosphorylation of p27,phosphorylation of p70 s6 kinase and phosphorylation of 4BP-1, animportant regulator of protein translation.

It is recognized that rapamycin reduces restenosis by inhibitingneointimal hyperplasia. However, there is evidence that rapamycin mayalso inhibit the other major component of restenosis, namely, negativeremodeling. Remodeling is a process whose mechanism is not clearlyunderstood but which results in shrinkage of the external elastic laminaand reduction in lumenal area over time, generally a period ofapproximately three to six months in humans.

Negative or constrictive vascular remodeling may be quantifiedangiographically as the percent diameter stenosis at the lesion sitewhere there is no stent to obstruct the process. If late lumen loss isabolished in-lesion, it may be inferred that negative remodeling hasbeen inhibited. Another method of determining the degree of remodelinginvolves measuring in-lesion external elastic lamina area usingintravascular ultrasound (IVUS). Intravascular ultrasound is a techniquethat can image the external elastic lamina as well as the vascularlumen. Changes in the external elastic lamina proximal and distal to thestent from the post-procedural timepoint to four-month and twelve-monthfollow-ups are reflective of remodeling changes.

Evidence that rapamycin exerts an effect on remodeling comes from humanimplant studies with rapamycin coated stents showing a very low degreeof restenosis in-lesion as well as in-stent. In-lesion parameters areusually measured approximately five millimeters on either side of thestent i.e. proximal and distal. Since the stent is not present tocontrol remodeling in these zones which are still affected by balloonexpansion, it may be inferred that rapamycin is preventing vascularremodeling.

The data in Table 1 below illustrate that in-lesion percent diameterstenosis remains low in the rapamycin treated groups, even at twelvemonths. Accordingly, these results support the hypothesis that rapamycinreduces remodeling.

Angiographic In-Lesion Percent Diameter Stenosis (%, Mean±SD and “n=”)in Patients Who Received a Rapamycin-Coated Stent

TABLE 1.0 Coating Post 4-6 month 12 month Group Placement Follow UpFollow Up Brazil 10.6 ± 5.7 (30) 13.6 ± 8.6 (30) 22.3 ± 7.2 (15)Netherlands 14.7 ± 8.8 22.4 ± 6.4 —

Additional evidence supporting a reduction in negative remodeling withrapamycin comes from intravascular ultrasound data that was obtainedfrom a first-in-man clinical program as illustrated in Table 2 below.

Matched IVUS Data in Patients Who Received a Rapamycin-Coated Stent

TABLE 2.0 4-Month 12-Month Follow-Up Follow-Up IVUS Parameter Post (n =)(n =) (n =) Mean proximal vessel area 16.53 ± 3.53 16.31 ± 4.36 13.96 ±2.26 (mm²) (27) (28) (13) Mean distal vessel area 13.12 ± 3.68 13.53 ±4.17 12.49 ± 3.25 (mm²) (26) (26) (14)

The data illustrated that there is minimal loss of vessel areaproximally or distally which indicates that inhibition of negativeremodeling has occurred in vessels treated with rapamycin-coated stents.

Other than the stent itself, there have been no effective solutions tothe problem of vascular remodeling. Accordingly, rapamycin may representa biological approach to controlling the vascular remodeling phenomenon.

It may be hypothesized that rapamycin acts to reduce negative remodelingin several ways. By specifically blocking the proliferation offibroblasts in the vascular wall in response to injury, rapamycin mayreduce the formation of vascular scar tissue. Rapamycin may also affectthe translation of key proteins involved in collagen formation ormetabolism.

Rapamycin used in this context includes rapamycin and all analogs,derivatives and congeners that bind FKBP12 and possess the samepharmacologic properties as rapamycin.

In a preferred embodiment, the rapamycin is delivered by a localdelivery device to control negative remodeling of an arterial segmentafter balloon angioplasty as a means of reducing or preventingrestenosis. While any delivery device may be utilized, it is preferredthat the delivery device comprises a stent that includes a coating orsheath which elutes or releases rapamycin. The delivery system for sucha device may comprise a local infusion catheter that delivers rapamycinat a rate controlled by the administrator.

Rapamycin may also be delivered systemically using an oral dosage formor a chronic injectible depot form or a patch to deliver rapamycin for aperiod ranging from about seven to forty-five days to achieve vasculartissue levels that are sufficient to inhibit negative remodeling. Suchtreatment is to be used to reduce or prevent restenosis whenadministered several days prior to elective angioplasty with or withouta stent.

Data generated in porcine and rabbit models show that the release ofrapamycin into the vascular wall from a nonerodible polymeric stentcoating in a range of doses (35-430 ug/15-18 mm coronary stent) producesa peak fifty to fifty-five percent reduction in neointimal hyperplasiaas set forth in Table 3 below. This reduction, which is maximal at abouttwenty-eight to thirty days, is typically not sustained in the range ofninety to one hundred eighty days in the porcine model as set forth inTable 4 below.

TABLE 3.0 Animal Studies with Rapamycin-coated stents. Values are mean ±Standared Error of Mean Neointimal Area % Change From Study DurationStent¹ Rapamycin N (mm²) Polyme Metal Porcine 98009 14 days Metal 8 2.04± 0.17 1X + rapamycin 153 μg 8 1.66 ± 0.17* −42% −19% 1X + TC300 +rapamycin 155 μg 8 1.51 ± 0.19* −47% −26% 99005 28 days Metal 10 2.29 ±0.21 9 3.91 ± 0.60** 1X + TC30 + rapamycin 130 μg 8 2.81 ± 0.34 +23%1X + TC100 + rapamycin 120 μg 9 2.62 ± 0.21 +14% 99006 28 days Metal 124.57 ± 0.46 EVA/BMA 3X 12 5.02 ± 0.62 +10% 1X + rapamycin 125 μg 11 2.84± 0.31* ** −43% −38% 3X + rapamycin 430 μg 12 3.06 ± 0.17* ** −39% −33%3X + rapamycin 157 μg 12 2.77 ± 0.41* ** −45% −39% 99011 28 days Metal11 3.09 ± 0.27 11 4.52 ± 0.37 1X + rapamycin 189 μg 14 3.05 ± 0.35  −1%3X + rapamycin/dex 182/363 μg 14 2.72 ± 0.71 −12% 99021 60 days Metal 122.14 ± 0.25 1X + rapamycin 181 μg 12 2.95 ± 0.38 +38% 99034 28 daysMetal 8 5.24 ± 0.58 1X + rapamycin 186 μg 8 2.47 ± 0.33** −53% 3X +rapamycin/dex 185/369 μg 6 2.42 ± 0.64** −54% 20001 28 days Metal 6 1.81± 0.09 1X + rapamycin 172 μg 5 1.66 ± 0.44  −8% 20007 30 days Metal 92.94 ± 0.43 1XTC + rapamycin 155 μg 10 1.40 ± 0.11* −52%* Rabbit 9901928 days Metal 8 1.20 ± 0.07 EVA/BMA 1X 10 1.26 ± 0.16  +5% 1X +rapamycin 64 μg 9 0.92 ± 0.14 −27% −23% 1X + rapamycin 196 μg 10 0.66 ±0.12* ** −48% −45% 99020 28 days Metal 12 1.18 ± 0.10 EVA/BMA 1X +rapamycin 197 μg 8 0.81 ± 0.16 −32% ¹Stent nomenclature: EVA/BMA 1X, 2X,and 3X signifies approx. 500 μg, 1000 μg, and 1500 μg total mass(polymer + drug), respectively. TC, top coat of 30 μg, 100 μg, or 300 μgdrug-free BMA; Biphasic; 2 × 1X layers of rapamycin in EVA/BMA spearatedby a 100 μg drug-free BMA layer. ²0.25 mg/kg/d × 14 d preceeded by aloading dose of 0.5 mg/kg/d × 3d prior to stent implantation. *p < 0.05from EVA/BMA control. **p < 0.05 from Metal; ^(#)Inflammation score: (0= essentially no intimal involvement; 1 = <25% intima involved; 2 = ≧25%intima involved; 3 = >50% intima involved).

TABLE 4.0 180 day Porcine Study with Rapamycin-coated stents. Values aremean ± Standard Error of Mean Neointimal % Change Inflam- Area Frommation Study Duration Stent¹ Rapamycin N (mm²) Polyme Metal Score #20007  3 days Metal 10 0.38 ± 0.06 1.05 ± 0.06 (ETP-2-002233-P) 1XTC +rapamycin 155 μg 10 0.29 ± 0.03 −24% 1.08 ± 0.04  30 days Metal 9 2.94 ±0.43 0.11 ± 0.08 1XTC + rapamycin 155 μg 10 1.40 ± 0.11* −52%* 0.25 ±0.10  90 days Metal 10 3.45 ± 0.34 0.20 ± 0.08 1XTC + rapamycin 155 μg10 3.03 ± 0.29 −12% 0.80 ± 0.23 1X + rapamycin 171 μg 10 2.86 ± 0.35−17% 0.60 ± 0.23 180 days Metal 10 3.65 ± 0.39 0.65 ± 0.21 1XTC +rapamycin 155 μg 10 3.34 ± 0.31  −8% 1.50 ± 0.34 1X + rapamycin 171 μg10 3.87 ± 0.28  +6% 1.68 ± 0.37

The release of rapamycin into the vascular wall of a human from anonerodible polymeric stent coating provides superior results withrespect to the magnitude and duration of the reduction in neointimalhyperplasia within the stent as compared to the vascular walls ofanimals as set forth above.

Humans implanted with a rapamycin coated stent comprising rapamycin inthe same dose range as studied in animal models using the same polymericmatrix, as described above, reveal a much more profound reduction inneointimal hyperplasia than observed in animal models, based on themagnitude and duration of reduction in neointima. The human clinicalresponse to rapamycin reveals essentially total abolition of neointimalhyperplasia inside the stent using both angiographic and intravascularultrasound measurements. These results are sustained for at least oneyear as set forth in Table 5 below.

TABLE 5.0 Patients Treated (N = 45 patients) with a Rapamycin-coatedStent Sirolimus FIM 95% Effectiveness Measures (N = 45 Patients, 45Lesions) Confidence Limit Procedure Success (QCA) 100.0% (45/45) [92.1%,100.0%]  4-month In-Stent Diameter Stenosis (%) Mean ± SD (N)  4.8% ±6.1% (30) [2.6%, 7.0%] Range (min, max) (−8.2%, 14.9%)  6-month In-StentDiameter Stenosis (%) Mean ± SD (N)  8.9% ± 7.6% (13) [4.8%, 13.0%]Range (min, max) (−2.9%, 20.4%) 12-month In-Stent Diameter Stenosis (%)Mean ± SD (N)  8.9% ± 6.1% (15) [5.8%, 12.0%] Range (min, max) (−3.0%,22.0%)  4-month In-Stent Late Loss (mm) Mean ± SD (N)   0.00 ± 0.29 (30)[−0.10, 0.10] Range (min, max) (−0.51, 0.45)  6-month In-Stent Late Loss(mm) Mean ± SD (N)   0.25 ± 0.27 (13) [0.10, 0.39] Range (min, max)(−0.51, 0.91) 12-month In-Stent Late Loss (mm) Mean ± SD (N)   0.11 ±0.36 (15) [−0.08, 0.29] Range (min, max) (−0.51, 0.82)  4-monthObstruction Volume (%) (IVUS) Mean ± SD (N) 10.48% ± 2.78% (28) [9.45%,11.51%] Range (min, max) (4.60%, 16.35%)  6-month Obstruction Volume (%)(IVUS) Mean ± SD (N)  7.22% ± 4.60% (13) [4.72%, 9.72%], Range (min,max) (3.82%, 19.88%) 12-month Obstruction Volume (%) (IVUS) Mean ± SD(N)  2.11% ± 5.28% (15) [0.00%, 4.78%], Range (min, max) (0.00%, 19.89%) 6-month Target Lesion Revascularization (TLR)  0.0% (0/30) [0.0%, 9.5%]12-month Target Lesion Revascularization  0.0% (0/15) [0.0%, 18.1%](TLR) QCA = Quantitative Coronary Angiography SD = Standard DeviationIVUS = Intravascular Ultrasound

Rapamycin produces an unexpected benefit in humans when delivered from astent by causing a profound reduction in in-stent neointimal hyperplasiathat is sustained for at least one year. The magnitude and duration ofthis benefit in humans is not predicted from animal model data.Rapamycin used in this context includes rapamycin and all analogs,derivatives and congeners that bind FKBP12 and possess the samepharmacologic properties as rapamycin.

These results may be due to a number of factors. For example, thegreater effectiveness of rapamycin in humans is due to greatersensitivity of its mechanism(s) of action toward the pathophysiology ofhuman vascular lesions compared to the pathophysiology of animal modelsof angioplasty. In addition, the combination of the dose applied to thestent and the polymer coating that controls the release of the drug isimportant in the effectiveness of the drug.

As stated above, rapamycin reduces vascular hyperplasia by antagonizingsmooth muscle proliferation in response to mitogenic signals that arereleased during angioplasty injury. Also, it is known that rapamycinprevents T-cell proliferation and differentiation when administeredsystemically. It has also been determined that rapamycin exerts a localinflammatory effect in the vessel wall when administered from a stent inlow doses for a sustained period of time (approximately two to sixweeks). The local anti-inflammatory benefit is profound and unexpected.In combination with the smooth muscle anti-proliferative effect, thisdual mode of action of rapamycin may be responsible for its exceptionalefficacy.

Accordingly, rapamycin delivered from a local device platform, reducesneointimal hyperplasia by a combination of anti-inflammatory and smoothmuscle anti-proliferative effects. Rapamycin used in this context meansrapamycin and all analogs, derivatives and congeners that bind FKBP12and possess the same pharmacologic properties as rapamycin. Local deviceplatforms include stent coatings, stent sheaths, grafts and local druginfusion catheters or porous balloons or any other suitable means forthe in situ or local delivery of drugs, agents or compounds.

The anti-inflammatory effect of rapamycin is evident in data from anexperiment, illustrated in Table 6, in which rapamycin delivered from astent was compared with dexamethasone delivered from a stent.Dexamethasone, a potent steroidal anti-inflammatory agent, was used as areference standard. Although dexamethasone is able to reduceinflammation scores, rapamycin is far more effective than dexamethasonein reducing inflammation scores. In addition, rapamycin significantlyreduces neointimal hyperplasia, unlike dexamethasone.

TABLE 6.0 Group Neointimal Rapamycin Area % Area Inflammation Rap N =(mm²) Stenosis Score Uncoated 8 5.24 ± 1.65  54 ± 19  0.97 ± 1.00 Dexamethasone 8 4.31 ± 3.02  45 ± 31  0.39 ± 0.24  (Dex) Rapamycin 72.47 ± 0.94* 26 ± 10* 0.13 ± 0.19* (Rap) Rap + Dex 6 2.42 ± 1.58* 26 ±18* 0.17 ± 0.30* *= significance level P < 0.05

Rapamycin has also been found to reduce cytokine levels in vasculartissue when delivered from a stent. The data in FIG. 1 illustrates thatrapamycin is highly effective in reducing monocyte chemotactic protein(MCP-1) levels in the vascular wall. MCP-1 is an example of aproinflammatory/chemotactic cytokine that is elaborated during vesselinjury. Reduction in MCP-1 illustrates the beneficial effect ofrapamycin in reducing the expression of proinflammatory mediators andcontributing to the anti-inflammatory effect of rapamycin deliveredlocally from a stent. It is recognized that vascular inflammation inresponse to injury is a major contributor to the development ofneointimal hyperplasia.

Since rapamycin may be shown to inhibit local inflammatory events in thevessel it is believed that this could explain the unexpected superiorityof rapamycin in inhibiting neointima.

As set forth above, rapamycin functions on a number of levels to producesuch desired effects as the prevention of T-cell proliferation, theinhibition of negative remodeling, the reduction of inflammation, andthe prevention of smooth muscle cell proliferation. While the exactmechanisms of these functions are not completely known, the mechanismsthat have been identified may be expanded upon.

Studies with rapamycin suggest that the prevention of smooth muscle cellproliferation by blockade of the cell cycle is a valid strategy forreducing neointimal hyperplasia. Dramatic and sustained reductions inlate lumen loss and neointimal plaque volume have been observed inpatients receiving rapamycin delivered locally from a stent. The presentinvention expands upon the mechanism of rapamycin to include additionalapproaches to inhibit the cell cycle and reduce neointimal hyperplasiawithout producing toxicity.

The cell cycle is a tightly controlled biochemical cascade of eventsthat regulate the process of cell replication. When cells are stimulatedby appropriate growth factors, they move from G₀ (quiescence) to the G1phase of the cell cycle. Selective inhibition of the cell cycle in theG1 phase, prior to DNA replication (S phase), may offer therapeuticadvantages of cell preservation and viability while retaininganti-proliferative efficacy when compared to therapeutics that act laterin the cell cycle i.e. at S, G2 or M phase.

Accordingly, the prevention of intimal hyperplasia in blood vessels andother conduit vessels in the body may be achieved using cell cycleinhibitors that act selectively at the G1 phase of the cell cycle. Theseinhibitors of the G1 phase of the cell cycle may be small molecules,peptides, proteins, oligonucleotides or DNA sequences. Morespecifically, these drugs or agents include inhibitors of cyclindependent kinases (cdk's) involved with the progression of the cellcycle through the G1 phase, in particular cdk2 and cdk4.

Examples of drugs, agents or compounds that act selectively at the G1phase of the cell cycle include small molecules such as flavopiridol andits structural analogs that have been found to inhibit cell cycle in thelate G1 phase by antagonism of cyclin dependent kinases. Therapeuticagents that elevate an endogenous kinase inhibitory protein^(kip) calledP27, sometimes referred to as P27^(kip1), that selectively inhibitscyclin dependent kinases may be utilized. This includes small molecules,peptides and proteins that either block the degradation of P27 orenhance the cellular production of P27, including gene vectors that cantransfact the gene to produce P27. Staurosporin and related smallmolecules that block the cell cycle by inhibiting protein kinases may beutilized. Protein kinase inhibitors, including the class of tyrphostinsthat selectively inhibit protein kinases to antagonize signaltransduction in smooth muscle in response to a broad range of growthfactors such as PDGF and FGF may also be utilized.

Any of the drugs, agents or compounds discussed above may beadministered either systemically, for example, orally, intravenously,intramuscularly, subcutaneously, nasally or intradermally, or locally,for example, stent coating, stent covering or local delivery catheter.In addition, the drugs or agents discussed above may be formulated forfast-release or slow release with the objective of maintaining the drugsor agents in contact with target tissues for a period ranging from threedays to eight weeks.

As set forth above, the complex of rapamycin and FKPB12 binds to andinhibits a phosphoinositide (PI)-3 kinase called the mammalian Target ofRapamycin or TOR. An antagonist of the catalytic activity of TOR,functioning as either an active site inhibitor or as an allostericmodulator, i.e. an indirect inhibitor that allosterically modulates,would mimic the actions of rapamycin but bypass the requirement forFKBP12. The potential advantages of a direct inhibitor of TOR includebetter tissue penetration and better physical/chemical stability. Inaddition, other potential advantages include greater selectivity andspecificity of action due to the specificity of an antagonist for one ofmultiple isoforms of TOR that may exist in different tissues, and apotentially different spectrum of downstream effects leading to greaterdrug efficacy and/or safety.

The inhibitor may be a small organic molecule (approximate mw<1000),which is either a synthetic or naturally derived product. Wortmanin maybe an agent which inhibits the function of this class of proteins. Itmay also be a peptide or an oligonucleotide sequence. The inhibitor maybe administered either sytemically (orally, intravenously,intramuscularly, subcutaneously, nasally, or intradermally) or locally(stent coating, stent covering, local drug delivery catheter). Forexample, the inhibitor may be released into the vascular wall of a humanfrom a nonerodible polymeric stent coating. In addition, the inhibitormay be formulated for fast-release or slow release with the objective ofmaintaining the rapamycin or other drug, agent or compound in contactwith target tissues for a period ranging from three days to eight weeks.

As stated previously, the implantation of a coronary stent inconjunction with balloon angioplasty is highly effective in treatingacute vessel closure and may reduce the risk of restenosis.Intravascular ultrasound studies (Mintz et al., 1996) suggest thatcoronary stenting effectively prevents vessel constriction and that mostof the late luminal loss after stent implantation is due to plaquegrowth, probably related to neointimal hyperplasia. The late luminalloss after coronary stenting is almost two times higher than thatobserved after conventional balloon angioplasty. Thus, inasmuch asstents prevent at least a portion of the restenosis process, the use ofdrugs, agents or compounds which prevent inflammation and proliferation,or prevent proliferation by multiple mechanisms, combined with a stentmay provide the most efficacious treatment for post-angioplastyrestenosis.

The local delivery of drugs, agents or compounds from a stent has thefollowing advantages; namely, the prevention of vessel recoil andremodeling through the scaffolding action of the stent and the drugs,agents or compounds and the prevention of multiple components ofneointimal hyperplasia. This local administration of drugs, agents orcompounds to stented coronary arteries may also have additionaltherapeutic benefit. For example, higher tissue concentrations would beachievable than that which would occur with systemic administration,reduced systemic toxicity, and single treatment and ease ofadministration. An additional benefit of drug therapy may be to reducethe dose of the therapeutic compounds, thereby limiting their toxicity,while still achieving a reduction in restenosis.

There are a multiplicity of different stents that may be utilizedfollowing percutaneous transluminal coronary angioplasty. Although anynumber of stents may be utilized in accordance with the presentinvention, for simplicity, one particular stent will be described inexemplary embodiments of the present invention. The skilled artisan willrecognize that any number of stents may be utilized in connection withthe present invention.

A stent is commonly used as a tubular structure left inside the lumen ofa duct to relieve an obstruction. Commonly, stents are inserted into thelumen in a non-expanded form and are then expanded autonomously, or withthe aid of a second device in situ. A typical method of expansion occursthrough the use of a catheter-mounted angioplasty balloon which isinflated within the stenosed vessel or body passageway in order to shearand disrupt the obstructions associated with the wall components of thevessel and to obtain an enlarged lumen. As set forth below,self-expanding stents may also be utilized.

FIG. 2 illustrates an exemplary stent 100 which may be utilized inaccordance with an exemplary embodiment of the present invention. Theexpandable cylindrical stent 100 comprises a fenestrated structure forplacement in a blood vessel, duct or lumen to hold the vessel, duct orlumen open, more particularly for protecting a segment of artery fromrestenosis after angioplasty. The stent 100 may be expandedcircumferentially and maintained in an expanded configuration, that iscircumferentially or radially rigid. The stent 100 is axially flexibleand when flexed at a band, the stent 100 avoids anyexternally-protruding component parts.

The stent 100 generally comprises first and second ends with anintermediate section therebetween. The stent 100 has a longitudinal axisand comprises a plurality of longitudinally disposed bands 102, whereineach band 102 defines a generally continuous wave along a line segmentparallel to the longitudinal axis. A plurality of circumferentiallyarranged links 104 maintain the bands 102 in a substantially tubularstructure. Essentially, each longitudinally disposed band 102 isconnected at a plurality of periodic locations, by a shortcircumferentially arranged link 104 to an adjacent band 102. The waveassociated with each of the bands 102 has approximately the samefundamental spatial frequency in the intermediate section, and the bands102 are so disposed that the wave associated with them are generallyaligned so as to be generally in phase with one another. As illustratedin the figure, each longitudinally arranged band 102 undulates throughapproximately two cycles before there is a link to an adjacent band.

The stent 100 may be fabricated utilizing any number of methods. Forexample, the stent 100 may be fabricated from a hollow or formedstainless steel tube that may be machined using lasers, electricdischarge milling, chemical etching or other means. The stent 100 isinserted into the body and placed at the desired site in an unexpandedform. In one embodiment, expansion may be effected in a blood vessel bya balloon catheter, where the final diameter of the stent 100 is afunction of the diameter of the balloon catheter used.

It should be appreciated that a stent 100 in accordance with the presentinvention may be embodied in a shape-memory material, including, forexample, an appropriate alloy of nickel and titanium. In thisembodiment, after the stent 100 has been formed it may be compressed soas to occupy a space sufficiently small as to permit its insertion in ablood vessel or other tissue by insertion means, wherein the insertionmeans include a suitable catheter, or flexible rod. On emerging from thecatheter, the stent 100 may be configured to expand into the desiredconfiguration where the expansion is automatic or triggered by a changein pressure, temperature or electrical stimulation.

FIG. 3 illustrates an exemplary embodiment of the present inventionutilizing the stent 100 illustrated in FIG. 2. As illustrated, the stent100 may be modified to comprise a reservoir 106. Each of the reservoirsmay be opened or closed as desired. These reservoirs 106 may bespecifically designed to hold the drug, agent, compound or combinationsthereof to be delivered. Regardless of the design of the stent 100, itis preferable to have the drug, agent, compound or combinations thereofdosage applied with enough specificity and a sufficient concentration toprovide an effective dosage in the lesion area. In this regard, thereservoir size in the bands 102 is preferably sized to adequately applythe drug/drug combination dosage at the desired location and in thedesired amount.

In an alternate exemplary embodiment, the entire inner and outer surfaceof the stent 100 may be coated with various drug and drug combinationsin therapeutic dosage amounts. A detailed description of exemplarycoating techniques is described below.

Rapamycin or any of the drugs, agents or compounds described above maybe incorporated into or affixed to the stent in a number of ways andutilizing any number of biocompatible materials. In the exemplaryembodiment, the rapamycin is directly incorporated into a polymericmatrix and sprayed onto the outer surface of the stent. The rapamycinelutes from the polymeric matrix over time and enters the surroundingtissue. The rapamycin preferably remains on the stent for at least threedays up to approximately six months and more preferably between sevenand thirty days.

Any number of non-erodible polymers may be utilized in conjunction withrapamycin. In the exemplary embodiment, the polymeric matrix comprisestwo layers. The base layer comprises a solution ofethylene-co-vinylacetate and polybutylmethacrylate. The rapamycin isincorporated into this layer. The outer layer comprises onlypolybutylmethacrylate and acts as a diffusion barrier to prevent therapamycin from eluting too quickly and entering the surrounding tissues.The thickness of the outer layer or top coat determines the rate atwhich the rapamycin elutes from the matrix. Essentially, the rapamycinelutes from the matrix by diffusion through the polymer molecules.Polymers are permeable, thereby allowing solids, liquids and gases toescape therefrom. The total thickness of the polymeric matrix is in therange from about 1 micron to about 20 microns or greater. In a preferredexemplary embodiment, the base layer, including the polymer and drug hasa thickness in the range from about 8 microns to about 12 microns andthe outer layer has a thickness in the range from about 1 micron toabout 2 microns.

The ethylene-co-vinylacetate, polybutylmethacrylate and rapamycinsolution may be incorporated into or onto the stent in a number of ways.For example, the solution may be sprayed onto the stent or the stent maybe dipped into the solution. In a preferred embodiment, the solution issprayed onto the stent and then allowed to dry. In another exemplaryembodiment, the solution may be electrically charged to one polarity andthe stent electrically changed to the opposite polarity. In this manner,the solution and stent will be attracted to one another. In using thistype of spraying process, waste may be reduced and more control over thethickness of the coat may be achieved.

Since rapamycin works by entering the surrounding tissue, it ispreferably only affixed to the surface of the stent making contact withone tissue. Typically, only the outer surface of the stent makes contactwith the tissue. Accordingly, in a preferred embodiment, only the outersurface of the stent is coated with rapamycin. For other drugs, agentsor compounds, the entire stent may be coated.

It is important to note that different polymers may be utilized fordifferent stents. For example, in the above-described embodiment,ethylene-co-vinylacetate and polybutylmethacrylate are utilized to formthe polymeric matrix. This matrix works well with stainless steelstents. Other polymers may be utilized more effectively with stentsformed from other materials, including materials that exhibitsuperelastic properties such as alloys of nickel and titanium.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

1. A drug delivery device comprising: an intraluminal medical device,the intraluminal medical device including a stent having a fenestratedstructure, the stent comprising a plurality of bands and links defininga substantially tubular device with openings; a polymeric coatingaffixed to the bands and links of the fenestrated structure, thepolymeric coating including first and second layers; and a therapeuticdosage of rapamycin incorporated into the polymeric coating fortreatment of intimal hyperplasia, constrictive vascular remodeling, andinflammation caused by injury, the rapamycin being incorporated into thefirst layer of the polymeric coating, the first layer comprising asolution of ethylene-co-vinylacetate and polybutylmethacrylate, and thesecond layer, comprising polybutylmethacrylate and acting as a diffusionlayer, the first layer having a thickness in the range from about eightmicrons to about twelve microns and the second layer having a thicknessin the range from about one micron to about two microns, the rapamycinbeing configured for release over a period of about seven to thirty daysand having a dosage in the range from about 35 to 430 micrograms per 15to 18 mm length stents thereby producing a peak 50 to 55 percentreduction in neointimal hyperplasia.